<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
        <span v-for="(item,index) in dots" class="dot" :class="{'active':currentPageIndex == index}"></span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
  import {addClass} from 'common/js/dom'
  import BScroll from 'better-scroll'
  export default {
    name: 'slider',
    props: {
      loop: {
        type: Boolean,
        default: true
      },
      autoPlay: {
        type: Boolean,
        default: true
      },
      interval: {
        type: Number,
        default: 4000
      }
    },
    data() {
      return {
        dots: [],
        children:0,
        currentPageIndex: 0
      }
    },
    mounted() {
      this.$nextTick(()=>{
        this._setSliderWidth();
        this._initDots();
        this._initSlider();
        if(this.autoPlay){
          this._play();
        }
      })
    },
    methods: {
      _setSliderWidth() {
        this.children = this.$refs.sliderGroup.children
        let width = 0
        let sliderWidth = this.$refs.slider.clientWidth
        for (let i = 0; i < this.children.length; i++) {
          let child = this.children[i]
          addClass(child, 'slider-item')
          child.style.width = sliderWidth + 'px'
          width += sliderWidth
        }
        if(this.loop == true){
          width += 2*sliderWidth
        }
        this.$refs.sliderGroup.style.width = width + 'px'
      },
      _initDots(){
        this.dots =  new Array(this.children.length)
      },
      _play(){
          let pageIndex = this.currentPageIndex+1
          // if(this.loop){
          //   pageIndex+=1
          // }
          this.timer = setTimeout(() => {
            console.log(this.currentPageIndex)
            this.sliders.goToPage(pageIndex,0,400)
          }, this.interval);

          if(this.currentPageIndex == 4){
            this.currentPageIndex == 0
          }
      },
      _initSlider(){
        this.sliders = new BScroll( this.$refs.slider,{
          //横向滚动
          scrollX: true,
          //纵向滚动
          scrollY: false,
          //惯性
          momentum: false,
          //遇到了问题无法克隆出dom元素，后因为是初始化参数更改导致
          snap: {
            loop: this.loop,
            threshold: 0.3,
            speed: 400
          },
          click: true
        })

        this.sliders.on('scrollEnd',()=>{
          let pageIndex = this.sliders.currentPage.pageX;
          //如果是轮播
          if(this.loop){
            pageIndex -=1
          }
          this.currentPageIndex = pageIndex

          if(this.autoPlay){
            clearTimeout(this.timer)
            this._play();
          }
        })
      }
    }
  }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  .slider
    min-height: 1px
    .slider-group
      position: relative
      overflow: hidden
      white-space: nowrap
      .slider-item
        float: left
        box-sizing: border-box
        overflow: hidden
        text-align: center
        a
          display: block
          width: 100%
          overflow: hidden
          text-decoration: none
        img
          display: block
          width: 100%
    .dots
      position: absolute
      right: 0
      left: 0
      bottom: 12px
      text-align: center
      font-size: 0
      .dot
        display: inline-block
        margin: 0 4px
        width: 8px
        height: 8px
        border-radius: 50%
        background: $color-text-l
        &.active
          width: 20px
          border-radius: 5px
          background: $color-text-ll
</style>